While not particularly known for its strength, the ubiquitous 8.25-inchrearend found its way under a whole slew of cars and trucks. Definitelynot as sexy as the 83/4, a drop-in-style differential featuring theconvenience of easy gear swaps or the nuclear bomb-proof Dana 60, butthis Salisbury-style differential is plentiful and reasonably strongwhen healthy. In a perfect world each and every one of us could affordto replace that modest 81/4 with one of Ma Mopar's beefier offerings,but we most certainly don't live in a perfect world. What to do then?It's simple--give the folks at Randy's Ring and Pinion a call and orderthe parts necessary to reinforce your 8.25.
You will recall that our Project Stealth Bomber '89 Diplomat police carwas being prep'd for the Nevada Open Road Challenge last May. We decidednot to take our chances on the stock physically abused unit out back,and instead opted to freshen it up with a new sure grip and an eventaller final drive ratio. Equipped from the factory with a 2.94 opendiff, we calculated our gear ratio based upon cruising speed versus rpm.With a 28-inch tall tire and a 2.94 gear ratio, 110 mph would require4,500 rpm while the same speed with a 2.76 gear and the aforementionedtires drops cruising rpm to a leisurely 4,000 rpm. So, we opted for the2.7s. We also took the opportunity to install an Auburn limited slipunit. The experts at Ramjet Rear End Repair were given the stage toperform the task of bringing the Stealth Bomber's rearend up to speed.
Randy's ring and Pinion offers...
Randy's ring and Pinion offers a complete line of products for the8.25-inch rearend. Randy provided us with axle bearings and seals, anAuburn limited slip, as well as their very own Yukon brandring-and-pinion.
Before the main caps can be...
Before the main caps can be unbolted, the retaining pin must be removed,as well as the bolts holding the lugs. (When the main caps are off, itis a good idea to mark them with a punch so that you know where to putthem.)
Now the entire carrier can...
Now the entire carrier can come out. Our Diplomat was equipped with anopen 2.94 rearend--not the object of performance dreams.
(above & right) Next, we unbolted...
(above & right) Next, we unbolted the ring gear from the carrier. Be aware that it is aright-hand thread. Once unbolted, we knocked the gear off the case witha punch. Here, Eddie Hernandez gets the job done.
The pinion is next on the...
The pinion is next on the agenda. It required a 11/4-inch socket and animpact wrench. We used an aluminum punch to push the pinion out and theseal.
The spider gears exhibited...
The spider gears exhibited some wear after years of abuse totingcriminals.
Eddie, our point man, reused...
Eddie, our point man, reused the original pinion shim as a startingpoint.
We opted for an Auburn cone-style...
We opted for an Auburn cone-style limited slip unit. These pieces arenot rebuildable once you wear them out. You simply replace 'em.
Eddie has been in the business...
Eddie has been in the business so long he has made a number of toolsspecifically for these applications, such as this bearing tool. Here,the carrier bearings are installed.
(above & right) The inner...
(above & right) The inner pinion race was installed by lightly tapping it in. The outerpinion race was next. We slide the outer pinion bearing in afterlightly oiling it. Then we put some white grease inside the pinion seal,tapped it in with a hammer, and we were done with the housing and couldmove on to assembling the carrier.
Before assembly, Eddie checked...
Before assembly, Eddie checked the new gears thoroughly as they may needto be deburred a bit with a grinding disc. This is normally the casewith new gears and not a production flaw.
A shop press was employed...
A shop press was employed for pressing on the pinion bearing. Afterinspecting the ring gear, it was bolted on at 50-inch-pounds.
(above & right) The pinion...
(above & right) The pinion went in first by lubing up the pinion bearing with oil, aswell as the splines. We started the splines on the yoke by lightlytapping it with a hammer. Then we greased the pinion nut. The pinion nuthas to crush the crush sleeve. This must be done very carefully. If yougo too far, you can't go back. The pinion ultimately should requirebetween 15- and 20-inch-pounds to turn. Guys like Eddie can spin it byhand and tell if it's tight or just right.
(above & next three photos)...
(above & next three photos) We oiled the carrier bearings, stuck in the adjusters, and bolted in themain caps. We installed the main caps carefully as sometimes theadjusters are crooked, and we didn't want to damage them.
Our Auburn carrier hit the...
Our Auburn carrier hit the housing requiring some grinding. So wecovered the pinion with a wet rag to catch the particles of metal. Justa little clearancing was required.
A yellow pattern maker was...
A yellow pattern maker was used to check how the gears mesh.
A dial indicator is used for...
A dial indicator is used for checking the back-lash (the distancebetween the pinion and the ring gear). In this instance, it was too muchat .014-inch. We reduced the back-lash and rechecked the pattern onceagain. Still no good as the gears should mesh more to the center. Thecarrier needed to be removed to change the pinion depth with shims. Theoriginal shim checked out at .027-inch, so we went with one thatdisplaces .024-inch. That did the trick.
After the diff was buttoned...
After the diff was buttoned back up, we filled the carrier with RoyalPurple gear lube. Synthetic gear oil has a greater resistance to heatand better lubricating qualities than its dinosaur-based cousin. Justwhat the doctor ordered for our sustained high-speed race last May.